1. Field of the Invention
The present invention relates generally to a variable damping force shock absorber for an automotive vehicle. More specifically, the invention relates to a reverse installation type shock absorber designed to be connected to a suspension member, such as suspension arm, suspension link or so forth, at the lower end of a piston rod and for variation of damping characteristics depending upon piston stroke.
2. Description of the Background Art
Such reverse installation type shock absorber has been disclosed in Japanese Patent First (unexamined) Publication No. 58-97334, for example. The shown shock absorber is designed for installation between a vehicular body and a suspension member which rotatably supports a vehicular wheel, in reversed manner to the usual shock absorber. The shock absorber includes a cylinder tube, a piston thrustingly or slidingly disposed within the internal space of the cylinder tube, and a strut tube thrustingly and slidingly supporting the cylinder tube. The top end of the cylinder tube is connected to a vehicular body. On the other hand, a piston rod extends downwardly from the bottom of cylinder tube for connection with the suspension member.
Such prior proposed reverse installation type shock absorber is defective in some aspects. For instance, the prior proposed shock absorber is so designed as to permit fluid flow from an upper fluid chamber to a lower fluid chamber via a predetermined bounding stroke fluid path and from the upper fluid chamber to an annular reservoir chamber defined between the cylinder tube and the strut tube. For this structure, the flow restriction magnitude for the fluid from the upper fluid chamber and to the lower fluid chamber cannot be great enough to provide satisfactorily high damping characteristics due possibly to cavitation. As a result, variation range of the damping characteristics is strictly limited. The cylinder tube and the strut tube may be subject of forces transverse to the axis thereof. For this reason, the cylinder tube may be required to have not only a high precision level in production for assuring smooth motion of the piston but also sufficiently high strength for resisting against the transverse forces. This could clearly cause high costs in production.